Ucon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ucon clear sky chart from 2005-11-06 to 2024-12-02.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	7% 8% 3 6% 4 4 4 3 5% 6% 50%	105487
	Night	9% 10% 3 7% 4 4 4 3 5% 7% 45%	102844
Transparency	Day	34% 5% 10% 21% 19% 11%	105235
	Night	38% 6% 12% 20% 16% 9%	102684
Seeing	Day	13% 11% 24% 28% 18% 6%	15387
	Night	14% 7% 20% 38% 19% 2	25019

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	13% 21% 7% 12% 4 4 4 3 5% 7% 22%	2447
	11th to 20th	Day	13% 16% 6% 12% 5% 4 3 3 4 5% 28%	2611
	21st to end	Day	18% 20% 5% 10% 4 3 3 3 4 5% 24%	3146
February	1st to 10th	Day	12% 16% 5% 11% 5% 5% 5% 5% 5% 6% 26%	1710
	11th to 20th	Day	13% 14% 6% 10% 5% 5% 5% 3 6% 6% 28%	1674
	21st to end	Day	8% 16% 5% 11% 5% 5% 4 4 5% 6% 32%	1570
March	1st to 10th	Day	9% 14% 5% 10% 6% 5% 4 3 5% 6% 34%	3310
	11th to 20th	Day	7% 10% 2 6% 4 3 4 3 4 6% 52%	3490
	21st to end	Day	11% 14% 6% 12% 6% 6% 5% 4 6% 6% 23%	3825
April	1st to 10th	Day	10% 12% 4 7% 5% 4 5% 4 7% 8% 36%	2160
	11th to 20th	Day	7% 10% 3 7% 4 4 3 4 6% 7% 43%	2437
	21st to end	Day	9% 10% 2 8% 4 4 4 4 6% 8% 40%	2470
May	1st to 10th	Day	11% 9% 3 7% 5% 3 4 4 5% 7% 42%	4110
	11th to 20th	Day	4 4 2 5% 4 4 4 4 6% 8% 56%	4071
	21st to end	Day	9% 8% 2 6% 4 4 5% 4 5% 7% 47%	4790
June	1st to 10th	Day	8% 4 2 5% 5% 4 5% 5% 7% 9% 47%	2785
	11th to 20th	Day	8% 5% 2 6% 3 4 4 3 6% 7% 53%	2850
	21st to end	Day	2 2 1 3 2 3 3 3 4 6% 71%	2850
July	1st to 10th	Day	1 2 1 2 2 2 2 3 4 5% 76%	4712
	11th to 20th	Day	1 2 1 3 3 2 3 3 5% 6% 71%	4396
	21st to end	Day	3 2 1 3 3 4 3 3 5% 7% 67%	4454
August	1st to 10th	Day	4 3 1 5% 3 3 5% 4 6% 8% 60%	4092
	11th to 20th	Day	3 2 1 2 2 3 3 3 4 7% 70%	4028
	21st to end	Day	2 2 1 3 3 3 3 3 5% 5% 71%	4521
September	1st to 10th	Day	4 3 1 3 2 3 2 3 4 5% 70%	2208
	11th to 20th	Day	7% 4 1 4 3 3 3 3 4 7% 61%	2090
	21st to end	Day	7% 4 1 3 2 3 2 2 5% 6% 64%	2090
October	1st to 10th	Day	7% 4 2 4 2 3 3 2 3 4 66%	3307
	11th to 20th	Day	6% 5% 2 5% 3 4 3 2 4 5% 62%	3150
	21st to end	Day	8% 9% 3 7% 4 4 5% 4 5% 7% 46%	3286
November	1st to 10th	Day	13% 12% 3 6% 4 3 4 3 4 6% 42%	1764
	11th to 20th	Day	11% 12% 3 7% 4 4 4 4 6% 8% 38%	1665
	21st to end	Day	10% 14% 4 7% 5% 4 4 3 4 5% 41%	1600
December	1st to 10th	Day	14% 14% 5% 11% 5% 4 3 3 5% 5% 31%	1528
	11th to 20th	Day	15% 15% 6% 12% 6% 5% 4 4 4 7% 23%	1848
	21st to end	Day	11% 14% 4 8% 5% 4 4 3 5% 8% 34%	2442
January	1st to 10th	Night	11% 18% 6% 12% 4 4 3 3 4 8% 25%	4525
	11th to 20th	Night	17% 23% 5% 9% 5% 3 3 3 4 6% 22%	4347
	21st to end	Night	21% 21% 5% 9% 4 3 3 2 4 7% 20%	4521
February	1st to 10th	Night	14% 16% 4 9% 6% 5% 4 3 5% 6% 28%	2470
	11th to 20th	Night	13% 15% 5% 8% 5% 4 4 3 4 6% 33%	2390
	21st to end	Night	8% 15% 7% 12% 5% 5% 4 4 5% 8% 28%	1884
March	1st to 10th	Night	8% 13% 4 9% 6% 5% 4 4 5% 8% 34%	3564
	11th to 20th	Night	5% 8% 3 5% 4 4 4 4 5% 10% 50%	3490
	21st to end	Night	9% 12% 3 8% 5% 5% 5% 5% 7% 9% 32%	3828
April	1st to 10th	Night	10% 11% 3 7% 5% 4 4 3 6% 8% 38%	2016
	11th to 20th	Night	8% 10% 2 7% 5% 5% 5% 4 5% 7% 41%	1691
	21st to end	Night	9% 8% 2 7% 4 4 4 3 6% 7% 46%	1710
May	1st to 10th	Night	9% 10% 3 7% 5% 4 4 3 6% 6% 43%	2860
	11th to 20th	Night	5% 4 2 4 3 4 5% 4 6% 9% 55%	2834
	21st to end	Night	9% 7% 2 6% 4 4 5% 4 6% 8% 46%	2795
June	1st to 10th	Night	7% 4 1 5% 5% 4 6% 4 7% 9% 49%	1390
	11th to 20th	Night	8% 5% 3 6% 4 3 2 4 5% 7% 53%	1330
	21st to end	Night	3 3 1 3 2 3 4 2 4 8% 68%	1330
July	1st to 10th	Night	3 2 1 3 3 3 3 3 5% 5% 72%	2243
	11th to 20th	Night	1 1 1 3 2 3 3 3 5% 8% 70%	2562
	21st to end	Night	2 2 1 3 3 3 4 4 6% 8% 64%	3109
August	1st to 10th	Night	3 2 2 4 3 3 4 3 6% 9% 61%	2847
	11th to 20th	Night	1 2 1 4 3 4 3 3 5% 7% 66%	2811
	21st to end	Night	3 3 1 3 2 2 2 2 4 4 72%	3146
September	1st to 10th	Night	4 3 1 4 2 3 3 3 4 4 69%	1968
	11th to 20th	Night	6% 4 2 4 3 3 4 3 5% 7% 60%	2090
	21st to end	Night	8% 4 1 3 3 2 2 3 4 5% 64%	2090
October	1st to 10th	Night	5% 3 1 3 3 2 2 2 3 5% 70%	3666
	11th to 20th	Night	10% 7% 2 5% 3 3 4 3 4 5% 55%	3778
	21st to end	Night	8% 9% 3 6% 4 4 5% 4 5% 8% 45%	4269
November	1st to 10th	Night	12% 10% 3 5% 3 3 4 4 5% 6% 45%	2535
	11th to 20th	Night	11% 12% 3 6% 5% 4 4 4 5% 6% 40%	2712
	21st to end	Night	10% 11% 4 7% 5% 4 4 3 5% 7% 40%	2800
December	1st to 10th	Night	12% 16% 5% 9% 6% 4 3 3 4 6% 32%	2687
	11th to 20th	Night	14% 17% 5% 9% 5% 4 4 3 4 6% 28%	3342
	21st to end	Night	12% 14% 5% 10% 4 4 5% 3 4 7% 32%	5214

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	62% 8% 13% 13% 3	2447
	11th to 20th	Day	59% 6% 15% 12% 7% 1	2611
	21st to end	Day	62% 8% 12% 12% 5% 1	3146
February	1st to 10th	Day	58% 9% 12% 16% 4 1	1710
	11th to 20th	Day	53% 9% 14% 17% 5% 1	1683
	21st to end	Day	52% 8% 15% 18% 6% 1	1570
March	1st to 10th	Day	50% 7% 15% 22% 6% 1	3310
	11th to 20th	Day	35% 5% 13% 33% 13% 1	3490
	21st to end	Day	58% 9% 16% 13% 4	3825
April	1st to 10th	Day	45% 8% 17% 17% 12% 2	2160
	11th to 20th	Day	38% 6% 12% 26% 14% 3	2440
	21st to end	Day	40% 7% 13% 26% 14% 1	2470
May	1st to 10th	Day	38% 6% 10% 24% 18% 4	4110
	11th to 20th	Day	24% 6% 10% 31% 21% 9%	4074
	21st to end	Day	34% 7% 10% 29% 17% 2	4790
June	1st to 10th	Day	31% 8% 13% 28% 18% 1	2785
	11th to 20th	Day	29% 6% 10% 21% 22% 12%	2850
	21st to end	Day	15% 3 6% 23% 33% 20%	2850
July	1st to 10th	Day	11% 2 5% 11% 30% 42%	4638
	11th to 20th	Day	14% 2 5% 9% 24% 46%	4321
	21st to end	Day	18% 3 5% 12% 33% 30%	4314
August	1st to 10th	Day	21% 4 7% 15% 29% 25%	4078
	11th to 20th	Day	15% 3 5% 20% 37% 20%	4067
	21st to end	Day	16% 3 5% 20% 29% 28%	4520
September	1st to 10th	Day	17% 4 6% 17% 32% 23%	2208
	11th to 20th	Day	23% 4 10% 24% 26% 13%	2090
	21st to end	Day	22% 3 8% 29% 28% 10%	2090
October	1st to 10th	Day	24% 3 7% 21% 35% 11%	3307
	11th to 20th	Day	26% 4 9% 36% 18% 6%	3150
	21st to end	Day	37% 6% 13% 26% 16% 1	3286
November	1st to 10th	Day	44% 5% 16% 22% 11% 1	1764
	11th to 20th	Day	43% 8% 18% 22% 6% 2	1665
	21st to end	Day	46% 5% 18% 21% 7% 1	1600
December	1st to 10th	Day	54% 7% 14% 15% 6% 2	1528
	11th to 20th	Day	61% 8% 12% 17% 2	1846
	21st to end	Day	48% 8% 16% 19% 8%	2442
January	1st to 10th	Night	58% 6% 11% 20% 4	4525
	11th to 20th	Night	63% 7% 12% 13% 4 1	4347
	21st to end	Night	62% 8% 14% 11% 4 1	4521
February	1st to 10th	Night	56% 8% 14% 16% 5% 1	2470
	11th to 20th	Night	51% 7% 14% 20% 7% 1	2391
	21st to end	Night	55% 7% 14% 16% 7% 1	1884
March	1st to 10th	Night	46% 9% 13% 23% 9% 1	3564
	11th to 20th	Night	30% 7% 17% 31% 14% 1	3490
	21st to end	Night	44% 10% 18% 23% 4 1	3828
April	1st to 10th	Night	43% 7% 15% 20% 13% 3	2016
	11th to 20th	Night	41% 6% 12% 24% 15% 2	1691
	21st to end	Night	36% 7% 13% 27% 17% 1	1710
May	1st to 10th	Night	38% 7% 11% 24% 17% 3	2860
	11th to 20th	Night	23% 6% 14% 28% 22% 7%	2835
	21st to end	Night	30% 8% 13% 26% 20% 3	2795
June	1st to 10th	Night	29% 9% 14% 22% 24% 2	1390
	11th to 20th	Night	30% 6% 9% 19% 25% 11%	1330
	21st to end	Night	16% 3 7% 19% 30% 26%	1330
July	1st to 10th	Night	14% 3 4 11% 23% 45%	2208
	11th to 20th	Night	13% 2 5% 11% 23% 47%	2514
	21st to end	Night	16% 4 6% 15% 27% 33%	3011
August	1st to 10th	Night	19% 3 6% 12% 29% 30%	2838
	11th to 20th	Night	18% 3 5% 20% 31% 23%	2838
	21st to end	Night	16% 3 6% 17% 27% 31%	3146
September	1st to 10th	Night	18% 3 6% 13% 31% 28%	1968
	11th to 20th	Night	24% 5% 8% 22% 24% 17%	2090
	21st to end	Night	22% 4 6% 25% 32% 11%	2090
October	1st to 10th	Night	19% 3 7% 20% 36% 15%	3666
	11th to 20th	Night	32% 4 7% 33% 17% 7%	3778
	21st to end	Night	37% 6% 13% 27% 18% 1	4269
November	1st to 10th	Night	39% 6% 15% 24% 14% 2	2535
	11th to 20th	Night	44% 7% 16% 24% 8% 2	2712
	21st to end	Night	45% 5% 18% 21% 10% 1	2800
December	1st to 10th	Night	54% 7% 17% 13% 7% 2	2687
	11th to 20th	Night	57% 7% 16% 17% 3	3343
	21st to end	Night	52% 7% 13% 17% 10% 1	5214

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	25% 9% 17% 23% 22% 4	180
	11th to 20th	Day	21% 7% 18% 28% 21% 4	202
	21st to end	Day	23% 12% 18% 31% 15% 2	297
February	1st to 10th	Day	22% 14% 27% 25% 11%	270
	11th to 20th	Day	22% 13% 23% 27% 13% 2	279
	21st to end	Day	19% 18% 28% 26% 7% 2	382
March	1st to 10th	Day	17% 19% 30% 24% 8% 1	460
	11th to 20th	Day	11% 15% 32% 26% 14% 2	460
	21st to end	Day	18% 21% 30% 24% 7%	506
April	1st to 10th	Day	19% 17% 28% 22% 10% 3	460
	11th to 20th	Day	16% 20% 31% 22% 10% 1	452
	21st to end	Day	17% 10% 30% 26% 13% 4	460
May	1st to 10th	Day	13% 14% 27% 27% 15% 5%	463
	11th to 20th	Day	11% 14% 27% 26% 17% 5%	488
	21st to end	Day	16% 9% 20% 26% 20% 8%	712
June	1st to 10th	Day	9% 11% 24% 28% 21% 8%	680
	11th to 20th	Day	14% 14% 25% 30% 15% 2	680
	21st to end	Day	4 6% 27% 32% 25% 6%	680
July	1st to 10th	Day	3 7% 22% 33% 27% 7%	656
	11th to 20th	Day	3 8% 25% 38% 20% 5%	484
	21st to end	Day	3 5% 21% 33% 28% 11%	531
August	1st to 10th	Day	5% 6% 25% 31% 26% 8%	487
	11th to 20th	Day	5% 4 21% 34% 24% 11%	477
	21st to end	Day	5% 10% 22% 28% 22% 13%	539
September	1st to 10th	Day	4 6% 24% 27% 28% 11%	490
	11th to 20th	Day	10% 10% 24% 27% 19% 9%	490
	21st to end	Day	9% 10% 22% 25% 23% 11%	490
October	1st to 10th	Day	12% 8% 16% 28% 25% 11%	385
	11th to 20th	Day	13% 13% 18% 22% 19% 16%	300
	21st to end	Day	19% 13% 18% 29% 18% 3	330
November	1st to 10th	Day	23% 9% 21% 25% 14% 8%	300
	11th to 20th	Day	16% 11% 21% 34% 14% 5%	300
	21st to end	Day	17% 9% 20% 32% 20% 2	300
December	1st to 10th	Day	23% 8% 18% 30% 15% 5%	273
	11th to 20th	Day	28% 7% 22% 26% 14% 2	246
	21st to end	Day	26% 12% 16% 24% 15% 7%	198
January	1st to 10th	Night	22% 8% 14% 35% 19% 2	827
	11th to 20th	Night	25% 7% 14% 33% 18% 3	760
	21st to end	Night	21% 6% 18% 37% 17% 2	836
February	1st to 10th	Night	24% 7% 23% 32% 13% 1	760
	11th to 20th	Night	21% 8% 19% 37% 13% 3	744
	21st to end	Night	14% 11% 24% 36% 13% 2	628
March	1st to 10th	Night	15% 10% 24% 36% 14% 1	760
	11th to 20th	Night	11% 8% 25% 37% 17% 2	760
	21st to end	Night	15% 8% 25% 38% 12% 1	836
April	1st to 10th	Night	16% 8% 26% 35% 14% 1	713
	11th to 20th	Night	13% 11% 31% 35% 9% 1	563
	21st to end	Night	13% 6% 24% 39% 16% 2	570
May	1st to 10th	Night	11% 8% 26% 35% 19% 1	570
	11th to 20th	Night	10% 6% 23% 33% 25% 3	561
	21st to end	Night	14% 6% 21% 39% 17% 3	617
June	1st to 10th	Night	8% 7% 21% 37% 25% 3	440
	11th to 20th	Night	9% 10% 27% 36% 17% 1	380
	21st to end	Night	3 3 19% 46% 24% 5%	380
July	1st to 10th	Night	3 1 16% 48% 28% 4	370
	11th to 20th	Night	2 1 15% 55% 26%	377
	21st to end	Night	3 1 18% 45% 31% 3	624
August	1st to 10th	Night	5% 4 16% 48% 27% 1	567
	11th to 20th	Night	3 2 18% 43% 31% 3	564
	21st to end	Night	5% 5% 16% 44% 28% 2	627
September	1st to 10th	Night	5% 3 18% 43% 27% 5%	662
	11th to 20th	Night	8% 4 16% 37% 29% 6%	760
	21st to end	Night	9% 4 17% 38% 25% 7%	760
October	1st to 10th	Night	11% 5% 18% 38% 26% 2	760
	11th to 20th	Night	13% 8% 18% 34% 23% 4	760
	21st to end	Night	11% 8% 21% 40% 16% 4	836
November	1st to 10th	Night	18% 8% 21% 33% 18% 2	780
	11th to 20th	Night	17% 10% 24% 36% 13% 1	912
	21st to end	Night	16% 8% 19% 36% 20% 2	1000
December	1st to 10th	Night	20% 8% 19% 38% 13% 2	960
	11th to 20th	Night	23% 9% 16% 37% 13% 1	950
	21st to end	Night	28% 8% 19% 32% 12% 1	1045

Page generated at 2024-11-29 08:43:06. Version ac07

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